There was a utility for creating new maps and campaigns. I found this site by the guy that made some of the maps, and I you can download the editor code.
http://chambcra.freeshell.org/It's not a trivial task to make a new map though.
If you try looking through the posts by Craigmire, you might find something about how to use it.
This is the post when he released his Grand Canyon map...
http://SimHQ.com/forum/ubbthreads.php/topics/2737058/1